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### Question: What causes Pulmonary atresia?
### Response: As with most congenital heart diseases, there is no known cause of pulmonary atresia. The condition is associated with another type of congenital heart defect called a patent ductus arteriosus (PDA).
Persons with pulmonary atresia may also have a poorly developed tricuspid valve. They may also have an underdeveloped right ventricle and abnormal blood vessels feeding the heart.
Pulmonary atresia may occur with or without a ventricular septal defect (VSD). If the person does not have a VSD, the condition is called pulmonary atresia with intact ventricular septum (PA/IVS). If the person has both problems, the condition is called pulmonary atresia with VSD. This is an extreme form of tetralogy of Fallot. Although both conditions are called pulmonary atresia, they are actually different defects.